This invention relates in general to stringing equipment for electrical conductors and more particularly to apparatus for grounding the conductors during conductor stringing operations.
As is well known, the stringing of single or a plurality of electrical conductors on electrical transmission towers oftentimes results in an induced charge being carried by the conductors as they are strung. This charge may arise due to static electricity, lightning, close proximity to existing power lines or other sources; however, it is nonetheless a dangerous and potentially fatal occurrence. Most conductor stringing block sheaves are lined with an elastomer which is non-conductive. It is, therefore, necessary to ground the conductor stringing blocks or in some manner to ground the conductor as it is passed through the block, thereby alleviating such hazardous conditions. Prior attempts at solving this problem are exemplified by U.S. Pat. Nos. 3,720,399 and 3,844,536. Both of these patents show auxiliary metallic rollers mounted proximal to the periphery of the sheaves of a stringing block so as to come into and remain in electrical contact with a plurality of electrical conductors being strung through the block. Both of these patents teach the use of a common ground roller shaft mounted on a pair of support arms which extend from the main frame of the block. Rotatably mounted on the common shaft is a plurality of ground rollers which are aligned with the conductor sheaves found in the block. Inasmuch as the conductors exhibit varying degrees of sag as they are being strung, it is necessary to allow the ground rollers to position themselves at various heights to insure adequate electrical contact between the roller and the conductor for the purpose of grounding the conductor. As noted the above mentioned patents both use a common shaft for all of the ground rollers. This common shaft is articulated at each end within the support arms such that the shaft may tilt when one end of the shaft is under a greater load than the other end thereof whereby the unloaded end is forced upwards and into contact with its associated conductor by the weight of the conductor lying across the other end. The U.S. Pat. No. 3,844,536 goes a step further and provides an eccentric bearing means between the roller shaft and the rollers. Two or more rollers are coupled by the eccentric bearing such that a weight disposed upon one of the rollers is transferred through the eccentric bearing to the coupled roller in order to position the coupled roller in contact with its associated conductor. It can readily be seen by a study of the construction of the devices that the interdependent structural mounting of these ground rollers inherently limits the motion capabilities of the individual ground rollers and therefore limits the ability of the ground rollers to maintain constant contact with the conductors thereby allowing the possibility for the conductor to be out of contact with the ground roller and therefore ungrounded.